1. Field of the Invention
The present invention relates to the assembly of disk drives for computer systems. More particularly, the present invention relates to a disk pack balancing station.
2. Description of the Prior Art
FIG. 1 shows an exploded view of a prior art disk drive comprising a disk pack assembly including a plurality of disks 2 clamped to a hub of a spindle motor 4 using a disk clamp 6, wherein a disk spacer 8 is inserted between the disks 2. The spindle motor 4 rotates the disks 2 while a plurality of heads 10 coupled to the distal ends of actuator arms 12 access respective disk surfaces (e.g., top and bottom disk surfaces). For clarity, only one head 10 and actuator arm 12 are shown in the example of FIG. 1; in practice, a number of actuator arms 12 and heads 10 are employed in an E-block configuration.
The actuator arms 12 are rotated about a pivot 14 by a voice coil motor (VCM) in order to actuate the heads 10 over the respective disk surfaces. The VCM comprises a voice coil 16 coupled to the base of the actuator arms 12 and one or more permanent magnets attached to a yoke 18. When the voice coil 16 is energized with current, the resulting magnetic flux interacts with the magnetic flux of the permanent magnets to generate a torque that rotates the actuator arms 12 about the pivot 14. A tang 20 attached to the actuator arms 12 interacts with a crash stop 22 to limit the stroke of the actuator arms 12, and also provides a latching mechanism (e.g., using a magnet) to maintain the actuator arms 12 in a latched position while the disk drive is powered down. Alternatively, the actuator arms 12 may be parked on a ramp mounted at the outer periphery of the disks 2 when the disk drive is powered down.
It is important to manufacture the disk pack assembly so that it is properly balanced to minimize disk wobble. One known technique for balancing the disk pack assembly is to use a disk pack balancing station which measures the disk pack imbalance and then inserts a wire of appropriate length and orientation to counteract the disk pack imbalance. A problem with this wire balance technique, however, is that it may require a large number of different length wires to compensate for a wide distribution of imbalance for the disk pack assemblies, which increases the manufacturing cost. The number of wires may be reduced by manufacturing the disks and spindle motor with a tighter tolerance, but this also increases the manufacturing cost.
There is, therefore, a need to improve disk pack balancing when manufacturing a disk drive.